Conventionally, a bar code representing various information by a striped pattern formed in a predefined combination of white lines and black lines with various thicknesses and a two-dimensional code capable of representing much information with a plurality of dots arranged vertically and horizontally are utilized in wide fields because reading and code recognition can easily be carried out.
For example, these barcodes and two-dimensional codes (which will be hereinafter referred to as codes collectively) are attached to packages of products and the like and are used for recognizing the products in a distribution process. In this case, the codes are read by means of a special code reader, camera or the like and are decoded into information configured from numerical values or letters. Recently, there is also provided the technology for displaying a code on a screen of a mobile terminal such as a portable telephone or a smartphone and reading the displayed code by a special code reader and decoding the displayed code.
In the case in which the code attached to the package of the product or the like is read by the camera, however, there is a problem in that the code cannot be read accurately if dirt sticks to the code itself or illumination light is contained in an image photographed by a camera in overlap with a code.
In the case in which a code displayed on a display screen of a mobile terminal is read, moreover, there is a problem in that the code cannot be read accurately if a scratch or dirt sticks to a display screen or the display screen partially causes mirror reflection by an incident angle of illumination light sent from a code reader.
In consideration of the latter problem, there is proposed the technology capable of accurately decoding a QR code (the registered trademark and so forth) displayed on a screen even if mirror reflection is caused on a screen of a mobile terminal or a scratch, dirt or the like sticks to the screen (for example, see Patent Document 1). In the technology described in the Patent Document 1, an image of the same QR code is displayed plural times on the screen at a time interval and the image to be displayed plural times is set to be displayed in a state in which it is rotated by 90 degrees at each time. Even if an unreadable portion occurs in a part of the QR code, thus, the portion which cannot be read in first display of the QR code can be read in second or succeeding display.
Moreover, the patent document 1 also describes that one QR code is divided into a plurality of parts and images of respective codes obtained by the division are displayed on the screen in order at a time interval. In this case, the respective codes thus divided are read by a code reader and are thus decoded and the data decoded from the respective codes are synthesized to obtain decode data on an original QR code.
Patent Document 1: Japanese Laid-Open Patent Publication No. 2004-54581